The invention relates to internal combustion engines with so-called side valve type, L-head type or flathead cylinder head layouts. In particular, the invention relates to an internal combustion engine with a side valve type cylinder head having two intake valves and an exhaust valve arranged as side valves.
In U.S. Pat. No. 1,687,082, a T-head type side valve arrangement is shown. Three valves are shown arranged across the cylinder from each other at both sides of the combustion chamber. Two intake valves are shown at these different sides. However, only one of the intake valves supplies an air/fuel mixture, while the other intake valve supplies air only. The layout for the valves precludes a compact combustion chamber and increases flow inefficiencies.
In U.S. Pat. No. 1,521,440, a valve arrangement is shown wherein an intake valve and an exhaust valve are located across from each other at a 45-degree angle to the cylinder. This type of arrangement requires two camshafts for the valve operations. This arrangement also precludes a compact combustion chamber and engine design.
In U.S. Pat. No. 2,179,143, an early overhead valve arrangement is shown. With this arrangement the cylinder head increases in weight and volume precluding a light engine and compact design.
In U.S. Pat. No. 2,244,214, an F-head engine arrangement is shown. This arrangement provides for an overhead exhaust valve and two side inlet valves. This arrangement requires significant overhead space for the operation of the overhead valve. The cylinder head is precluded from being compact by such a design.
Traditionally, side valve engines are characterized by low power output attributed to a two valve layout with valves that are masked over nearly 180xc2x0 C. of their circumference and with a low cylinder head height which prevents the valves, particularly the intake valve, lifting to a conventional level of some 33% of its inner seat diameter. The cylinder head has a high surface-volume ratio of its combustion chamber exacerbating the heat loss from the combustion chamber during the combustion period, reducing power output and raising hydrocarbon emissions. Additionally, to reduce the chamber volume in the two-valve layout, the mouth into the side valve chest is reduced in area giving an excessive squish effect, which increases the pumping losses into, and out of, the chamber, hence further lowering the attained engine torque.
The plan view of a typical side valve combustion chamber resembles a xe2x80x9cbonexe2x80x9d with the two valves at either end. This layout is hardly ideal from a combustion standpoint, making it prone to detonation at equal compression ratios with an overhead valve engine. The squish flow into the xe2x80x9cbonexe2x80x9d shape is a diffusing flow, i.e. it slows down as it travels. As the exhaust valve is the farthest point away from the combustion chamber, this leaves hot exhaust gas unscavenged by a fresh squish charge, and so, tends to cause xe2x80x9cknockingxe2x80x9d of the compressed charge. The xe2x80x9cbonexe2x80x9d shape also makes the optimum placement of a spark plug more problematic.
The close proximity of the hot exhaust valve to the cylinder bore also gives rise to bore distortion which increases the oil consumption rate of the engine and further raises the exhaust emissions of unburned hydrocarbons. This heat distortion reduces the life of the engine and eventually gives rise to a decrease in performance and to significant wear on the engine components. Known methods of overcoming the heat distortion are to locate the exhaust valve farther away from the combustion chamber thus exacerbating the inefficiencies of the cylinder head design, i.e. the exhaust valve is then smaller, or the cylinder head surface area increases. A spark plug located near the exhaust valve may also experience increased temperature effects due to the flow into the exhaust valve and reduce its life and its effectiveness.
Certain preferred embodiments of the invention have as a basis a problem of solving the inherent inefficiencies and above-stated problems related to a conventional two-valve side valve cylinder head arrangement and the prior art.
An object of the invention is to increase the performance and life of a side valve type engine while maintaining the beneficial characteristics of a side valve design, which side valve design is much smaller, lighter and more compact than an overhead valve or overhead cam design and very much cheaper and simpler to manufacture.
Another object according to certain preferred embodiments of the invention is to reduce or eliminate the heat distortion on the piston cylinder walls due to the close proximity of the exhaust port.
Another object according to certain preferred embodiments of the invention is to increase the volumetric efficiencies for a side valve type engine and reduce inherent throat restrictions of the valve circumference or the cylinder head, i.e. the xe2x80x9cmaskingxe2x80x9d of the valves.
Another object according to certain preferred embodiments of the invention is to provide a cylinder head and combustion chamber design that lends itself to a simple, effective placement of an ignition plug.
These problems are solved according to certain preferred embodiments of the invention by an at least three-valve side valve arrangement. A side-valve engine comprises at least one cylinder having a movable piston and at least two intake valves being located to one side of each of the at least one cylinder. Further advantages are provided by at least one exhaust valve being located to the one side of said each of the at least one cylinder. This arrangement allows for a compact combustion chamber and compact engine design.
In certain preferred embodiments, the intake valves are located between the piston cylinder and the exhaust valve. Preferably, the exhaust valve is located farther from the cylinder than the intake valves. The intake valves are arranged on respective sides of a radial line of the cylinder to the exhaust valve, and the intake valves are symmetrically arranged on the one side of the cylinder between the exhaust valve and the cylinder.
Preferably, the intake valves are positioned in the engine block to one side of the piston cylinder with the valves seating into the engine block substantially parallel to a radius of the piston cylinder. Valves stems operating substantially parallel to an axial extent of the piston cylinder allows for a more compact design of the engine.
A further advantage of certain preferred embodiments provides at least one exhaust valve being positioned radially farther away from the piston cylinder than the intake valves. Preferably, the exhaust valve is substantially centered on a radial centerline of the piston cylinder, and the intake valves are substantially symmetrical about the piston cylinder radial centerline. Such arrangement eliminates heat distortion to the piston cylinder walls by the exhaust valve and port due to the location of the exhaust valve and port away from these walls. The intake valves, and the metal bridge between these ports, also have some cooling effect to the exhaust valve and port.
In other contemplated embodiments, the cylinder head design allows for the exhaust valve being off the radial centerline of the piston cylinder and the intake valves being arranged non-symmetrically about the radial centerline and each other.
A three-valve arrangement according to certain preferred embodiments of the invention also provides a more regular shape and reduces or eliminates the cylinder head pumping restrictions inherent in a two-valve design. The design nearly eliminates throat or masking restrictions for the intake valves and considerably decreases the throat or masking restrictions for the exhaust valve. Both the intake and exhaust valves can be lifted to values conventional for an overhead valve or an overhead cam engine and, being possessed of similar discharge coefficients of flow, can breathe air and produce power equal to an equivalent overhead valve engine. The valve areas which are shrouded for the three-valve design are hence decreased and contribute to high volumetric efficiencies. The design also is beneficial to the combustion chamber shape. The combustion chamber shape provided is much more symmetrical and regular. The xe2x80x9cbonexe2x80x9d shape with its diffusing squish flow is eliminated. It is important to note that the diffuser shape is eliminated and replaced by a nozzle profile which permits a high recirculation velocity over the exhaust valve so that the xe2x80x9cknock promotingxe2x80x9d pockets of residual exhaust gas are removed. The regular shape of the chamber above the valves also lends itself to an effective location of a spark plug. The spark plug may be located about the radial centerline of the combustion cylinder and midway between the intake valves. The igniter/spark plug may also be arranged near the sidewall of the piston cylinder. The location of the intake valve flow also has a cooling effect on the spark plug and leaves fresh charge to promote good ignition.
The effective tumbling squishing characteristics allow a more efficient engine which can use higher compression ratios without incurring detonation. Bore distortion is severely decreased due to the placement of the exhaust valve and port away from the piston cylinder. The placement of the intake valves also allows a better shape for the intake runners or pipes leading to the valves, which shape yields high discharge coefficients for intake inflow of air. The design allows for the beneficial use of side valve cylinders and its accompanying small sized engine while considerably improving the overall efficiency over conventional side valve engines. The benefits of the design are higher compression ratios, longer life, improvements in power, torque, fuel consumption and emissions. The performance characteristics of such engine designs can match an equivalent two-valve overhead valve engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.